Multimerization of Drosophila sperm protein Mst77F causes a unique condensed chromatin structure.
Bottom Line: This binding results in structural reorganization of the domain, which induces interaction with an N-terminal region of the protein.Via putative cooperative effects Mst77F is induced to multimerize in this state causing DNA aggregation.In agreement, overexpression of Mst77F results in chromatin aggregation in fly sperm.
Affiliation: Laboratory of Chromatin Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.Show MeSH
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Mentions: To analyze whether Mst77F has autonomous effects on chromatin or requires cellular cofactors, we set up in vitro systems. First, we analyzed interaction of Mst77F with recombinant oligonucleosomal arrays reconstituted on the 12 × 200 bp x 601 DNA sequence (Figure 2A) (32). In co-precipitation experiments we detected association of the protein with chromatin that could not be saturated at 4-fold molar excess of the protein compared to histone octamers. We also noted that binding of increasing amounts of Mst77F did not cause eviction of any core histone from the chromatin fiber. Next, we analyzed the consequence of Mst77F binding for chromatin conformation. Addition of Mst77F was sufficient to impair MNase digestion of recombinant oligonucleosomal arrays (Figure 2B). While the effect was weaker compared to linker histone hH1.4, imaging of the oligonucleosomal arrays by atomic force microscopy clearly indicated significant chromatin compaction and aggregation induced by Mst77F (Figure 2C).
Affiliation: Laboratory of Chromatin Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.